St. Cloud doctor David Kroska tells his class of medical students that the job is often unpredictable. Now, he has an exceptional example of that.

In an on-call shift at the St. Cloud Hospital, Kroska delivered 13 babies in 24 hours last week — a record for both the veteran doctor and possibly even the hospital.

“I’ve never done that in my life,” said Kroska, a CentraCare Clinic obstetrician and gynecologist who also teaches at the University of Minnesota. “It was overwhelming that I’d delivered that many babies. That’s the nature of on-call — the unexpected.”

In his 32-year career, he estimates he’s delivered 6,000 babies. But never has he had so many babies in one night. In fact, hospital spokeswoman Deb Paul said, the hospital averages about seven births a day, or 2,600 births a year.

Yet, starting at 9 a.m. Sept. 12, Kroska had time to squeeze in only a 15-minute nap and reheated spaghetti as he rushed between rooms delivering seven baby boys and six baby girls, some less than 30 minutes apart.

“It was a very full night,” he said. “Sometimes two [mothers in labor] would walk in the door at a time.”

Kroska and his staff were so busy they didn’t even realize until the shift ended that he had surpassed his own record of 10 deliveries in 24 hours. He said it also exceeds the number of babies his 12 OB/GYN partners have delivered in that time.

What’s also extraordinary: None of the 13 babies were twins or triplets. All were at or close to full-term, except for one preemie, two months early. And two of the babies were delivered by Caesarean section. The most frazzled Kroska got was around 1 a.m., when two women were about to give birth at the same time — a “doubleheader,” he said; a senior resident had to step in to deliver one of the babies.

After more than three decades of delivering babies — the Collegeville father of eight even delivered one of his own kids when a doctor didn’t arrive in time — it was, he said, his busiest day on the job.

As for an explanation for the unusual bump in births, Kroska says it’s a medical mystery — one that will provide a valuable lesson to his medical students.

“If you go into OB, this is what you could get into,” he said he’ll tell them. “It’s random and unpredictable and you just go with the flow.”